The use of RF technology for recognizing items by means of RF tags has been well known for several decades. Examples of this technique include the tagging of animals for experimental purposes as well as tracking herds, pallets moving on the factory floor, the use of tags for inventory, automatically tendering highway tolls, tracking railway freight cars etc. The idea of using tags in place of bar codes at the checkout counter has also been proposal, most recently in public announcements by CSIR, in south Africa in conjunction with the British Technology Group (BTG). Here, it was shown that as many as 50 items in a shopping cart can be poled and registered in 1 second.
The concept of tagging items in supermarkets is described in U.S. Pat. No. 4,656,463 by Anders et al., European Patent Application 0 623,904 to Chenoweth et al., and European Patent Application 0 494,114 to Marsh et al. which are herein incorporated by reference in their entirety.
In Anders the tags have several applications; e.g., as a means for maintaining and tracking inventory on the shelves as items are removed by the customer. In addition, the market basket has an attached passive tag. Scanning is done by one or more antennas placed within the store at various positions. The antenna(s) send out interrogation signals over various time intervals. However, the main checkout is done at a counter through which the customer must pass prior to exiting the store. This method seems to require duplicate checking of objects in the store, i.e., a interrogation of the objects on the store shelf appears to be redundant with a final interrogation done at a check out counter. A necessary check out counter is also disclosed.
In Marsh, a shopping cart containing "transponders", presumably used to tag objects in the cart, is disclosed. An interrogator sends out an interrogation signal that causes the transponders to repeatedly transmit a response signal containing data identifying the transponder. Logic in each of the individual transponders is used to cease transmission of the individual transponder in response to interruptions in the interrogation signal that indicate the individual transponder has been identified. By doing this, it appears that the system can identify more than one transponder in a field of many transponders. However, the transponders are required to repeat transmission of their response signal to increase the probability of a successful reception (identification) by the interrogator. As the number of objects in the cart increases, it appears that the probability of a successful reception (identification) decreases. Furthermore, the interrogator is located at a "till" that the "trolley full of groceries" has to pass by in order to identify the transponders in the "trolley."
Chenoweth, a retail checkout system is disclosed that has a manual checkout device attached to a cart. However, each item selected has to be manually logged in by the shopper. This manual operation turns off an anti-theft tag on the selected object. Any object/item returned to the shelf must be manually logged out by the shopper. This process resets the anti-theft tag. Therefore, tracking and/or polling of the objects can only occur by manual customer action.
Other prior art describes carts that tender items as they are taken off the shelf and which subtract from the cart total if the item is put back on the shelf. However, there is no provision for constant periodic re-polling of the items. Thus, the customer must rely on the antenna at the shelf to subtract any items that are put back on the shelf. This is not as reliable or as assuring to the customer that the proper items are being polled in the final tally.